The invention relates to a device comprising two linkage mechanisms each having at least three bars of which a first and a second bar with the same length extend parallel to each other and are pivotably interconnected by at least a third bar, the two first and two third bars of both mechanisms are pivotably connected at a common main pivot, hinge points of the first bars lying away from the main pivot are independently movable along linear paths, the device is further provided with a tool comprising the main pivot.
By such a device which is known from U.S. Pat. No. 4,687,400 the tool comprises a gripper means having two claws. The main pivot is connected to both claws whilst at each claw one of the two pivots of the second and third bars are connected. By translating both hinge points in the same parallel vertical transport directions and over the same distance the tool is moved vertically. By translating only one of the hinge points the tool moves mainly in a horizontal direction. By moving at least one of the second bars, the claws of the gripper means are closed or opened.
The second bars are moved by translating the end of the second bars remote from the third bars in a vertical direction parallel to the transport direction of the hinge points of the first bars. Hereby the distance between said ends of the second bars and the hinge points change. This means that the first and second bars do not remain parallel, so that the control of the desired accurate movements is relatively complicated. Furthermore by the device according to U.S. Pat. No. 4,687,400 the tool cannot be rotated round the main pivot in order to rotate the object situated between the claws.
It is therefore an object of the present invention to provide a device whereby the tool cannot only be moved in at least two different directions but can also be rotated around the main pivot.
This object of the present invention is achieved in that the first and second bars of each mechanism are pivotably connected by a fourth bar, lying parallel to and having the same length as the third bar, the fourth bar is rotatable about the hinge point of the first bar, the pivot points of the third and second bars of the first and second mechanism are connected to the tool and a part of the tool respectively, whereby rotating the fourth bar of the first mechanism around the hinge point causes a rotation of the tool around the main pivot and rotating the fourth bar of the second mechanism around the hinge point causes rotation of the part of the tool around the main pivot.
In this patent application a bar should be considered as any connecting element which is pivotably connected between two pivots.
By rotating one of the fourth bars the tool as such is rotated whilst the part of the tool, for example the gripper means need not to be rotated with respect to the tool.
By moving the two hinge points and rotating the two fourth bars, the tool can be moved into/in two orthogonal directions, rotated round the main pivot and perform an additional feature, like opening or closing gripper means, rotating a gear connected to a manipulator and located in the tool etc.
An embodiment of the device according to the invention is characterized in that at least one linkage mechanism comprises a fifth bar lying parallel to and having the same length as the first bar, the first and fifth bar are pivotably connected by a sixth and seventh bar lying parallel to each other and having the same length, the sixth arm is pivotably connected to the first arm at the main pivot point and encloses an angle with the third arm.
In this manner the fourth bar can be rotated fully round the hinge point without having the risk that at the so called dead point, in which the third and fourth bar extends parallel to the first and second bar, the fourth bar continues to rotate in one direction whilst the third bar changes from the direction of rotation.
Another embodiment of the device according to the invention is characterized in that the fourth arm is pivotably connected to an angle doubling mechanism.
If at the input of the angle doubling mechanism a 90xc2x0 rotation is performed, the fourth arm will rotate over 180xc2x0.